General usesOutboard motors for a boat are developed as a self-contained unit with engine, subsidiary systems, and propeller, designed to be mounted at the stern (rear) of the craft. They are the most common motorized method of propelling small watercraft.As well as providing propulsion, outboards provide steering control, as they are designed to pivot over their mountings and thus control the orientation of the propeller. The transmission leg in the water also acts as a rudder even when the propeller is not providing power.When boats are out of service or being drawn through shallow waters, outboard motors can also be tipped forward over their mounts to elevate the propeller and transmission shaft out of the water to avoid accumulation of seaweed or hitting underwater hazards such as rocks.[edit] Types of motorsSmall outboard motors are truly self-contained, with integral fuel tanks and controls mounted on the body of the motor and steered by a "tiller" directly connected to the motor. Such small motors can weigh as little as 12 kilograms (approximately 26 pounds) and provide sufficient power to move a small dinghy at around 15 km/h (9 mph), far faster than possible with oars. They are highly portable, able to be removed by simply loosening their mounting clamps. Small outboards usually use a manual pull start ignition system while larger models often have electric start similar to a car.Manufacturers have produced large outboard designs, with sufficient power to be used on boats as long as 9 metres (30 feet) or more. Manufacturers have also produced electric outboards. These are used for specialised applications, notably trolling for bass in the US, where their quietness and zero emissions outweigh the range deficiencies shared with electric cars. Diesel outboards are also available, but their weight and cost make them impractical for most purposes.A few outboard motors have been produced with pump-jet propulsion replacing the conventional propeller. Like other types of pump-jet propulsion systems, they offer virtually no cavitation, giving the boat more maneuverability and the ability to operate in very shallow water. However, the low efficiency compared to propellers has seen them restricted to specialized applications.[edit] History and developmentsThe first practical outboard motor was created by Norwegian-American inventor Ole Evinrude in 1909.Historically, most outboards have used two-stroke engines fitted with a carburetor due to their simplicity (and consequent reliability), low cost, and high power-to-weight ratios - weight issues being particularly important as too much weight over the stern of boats tends to impede their handling. However, the high specific fuel consumption and high emissions associated with traditional carburated two-stroke engines has led to the development of more sophisticated engines. Most manufacturers have marketed four-stroke engines, often with computer controls, fuel injection, variable camshaft timing, multiple valves per cylinder, and supercharging. Others have focused on developing computer controlled direct-injected two stroke engines. Either of these designs can reduce fuel consumption and emissions markedly, especially at low engine speeds, albeit at the expense of greater cost and complexity.Marine engines also benefit from the ability to draw an unlimited supply of cooling water from the environment; this eliminates the need for radiators and cooling fans, lowering complexity and weight.edit] See also• Inboard motor• Air engine• Diesel• Sterndrive• Luxury yacht tenders[edit] External links

Inflatable boats at Horsea Island, England.An inflatable boat is a lightweight boat constructed with its sides and bow made of flexible tubes containing pressurised gas. For smaller boats, the floor and hull beneath it is often flexible. On boats longer than 3 metres/10 feet, the floor often consists of three to five rigid plywood or aluminium sheets fixed between the tubes but not joined rigidly together. Often the transom is rigid, providing a location and structure for mounting an outboard motor.Some inflatable boats have been designed to be disassembled and packed into in a small volume, so they can easily stored and transported to water when needed. This feature allows such boats to be used as liferafts for larger boats or aircraft, and for travel or recreational purposes.Other terms for inflatable boats are "rubber dinghy" or simply "inflatable."[edit] TypesInflatable boats may have rubber floors, either plain or inflatable, or they may include steel, wood or aluminium sheets for rigidity. The tubes are made of rubberised, synthetic sheets of Hypalon or PVC to provide light-weight and secure buoyancy. The tubes are often constructed in separate sections, each with a valve to add or remove air, to reduce the effect of a puncture.Some inflatable boats have an inflated keel to create a "groove" along the line of the hull improving the hull's wave cutting and turning performance. Due to the lightness, it is easy to cause an inflatable boat to start hydroplaning, thus making it faster than the engine would allow when the hull is operating in displacement mode.A growing use for inflatables is for white water rafting and kayaking, as well as in river, lake and ocean touring. Professional-level rafts and kayaks have existed for many years; since the late 1990s, more affordable inflatable rafts, kayaks (including sea kayaks) and canoes have been developed by European and North American companies. Typically these inflatable boats contain no rigid frame members, so they can be deflated, folded and stored in compact bags.[edit] RepairingShould a section puncture it can be repaired while still underway. More extensive inflatable boat repairs - due to pinholes, punctures, peeling, leaks or worn fabric - can be done in dry dock using two-stage synthetic rubber coatings (SRC).Subject to a great deal of wear and tear from the elements - both water and sun - inflatable boats are often replaced when they could be restored or even repaired. Products that aggressively adhere to the damaged Hypalon or PVC shell can fix virtually any surface damage through a unique chemical bonding between the undercoat and topcoat that permanently vulcanizes the two rubber coatings together to make the inflatable as good as new. However since the Hypalon material increases the cost of the inflatable up to 15% not all manufactures provide the option. Some, such as the Brig and the ZODIAC brand inflatable boat offer the option between the PVC or the Hypalon which is recommended for environments of increase heat and sunlight.

A ZODIAC brand inflatable boat is hoisted aboard an expedition cruise ship in Antarctic waters after ferrying passengers to shore.[edit] UsesInflatables are commonly between 2 and 7 metres (6 to 21 feet) long and are propelled by outboard motors of 5 to 80 horsepower (4 to 60 kW). Due to their speed, portability and weight, inflatable boats are used extensively as:-• rescue craft• dive boats for scuba diving• tenders for larger boats and ships in port and at sea• luxury yacht tenders• recreational water skiing• for racing• commercial or recreational fishing• for military purposes, such as transporting soldiers from a vessel to shoreInflatables up to 6 metres in length can be towed on trailers on the road.These boats are often used by special-operations units of the armed forces of several nations, for such purposes as landing on beaches or submarines. They have also be used by special-ops soldiers without government sponsorship, such as guerrillas, pirates, and terrorists.

A Sea Ealge inflatable jumping waves off the Hamptons[edit] History[edit] Early attemptsThere are ancient carved images of animal skins filled with air being used as one-man floats to cross rivers. They were inflated by mouth. (Sometimes these images have been wrongly described as ancient scuba.)In 1839 the Duke of Wellington tested the first inflatable pontoons.[edit] Rubber arrivesIn 1900 to 1910 the development of rubber manufacturing enabled attempts at producing circular rubber inflatable boats: in essence, modern-day coracles. These were only usable as rafts and could be propelled only by paddling, and they tended to crack at seams and folds due to imperfect manufacture of the rubber.[edit] Titanic and WWIWith the loss of the Titanic in 1912, and World War I losses of ships to submarine-launched torpedoes, the need for inflatable boats was plain.One cause of the loss of life on the Titanic was the lack of lifeboats. Even if every lifeboat had been completely filled with passengers and crew, there would have been no way to rescue more than half of all the people on board. The first SOLAS treaty was designed to avoid such a disaster happening again. One of its provisions was to ensure that vessels had enough lifeboats to provide every person aboard the vessel with a place. Putting this rule into effect was not difficult with cargo ships: they had small crews and plenty of deck space. Passenger ships had to stack lifeboats on top of each other to able to carry enough to accommodate the large number of passengers and crew. Warships also had large crews and little deck space.Between the two World Wars, Goodyear found a way to join rubber to other materials. They made life rafts of square-shaped inflated rubber tubes with a rigid floor. Such rafts were to be stacked vertically aboard warships, usually standing on deck and leaning against deck-houses. But conservative thinking from navies held back this new idea.Pierre Debroutelle's 1937 design was the first known to have its inflatable tube in a U-shape. It was the first boat of its kind to be certified by the French Navy. Its added wooden transom was patented on 10 August 1943. This version was the predecessor of today's inflatable sports and pleasure boats.[edit] World War IIWorld War II changed everything. Submarine warfare in the Battle of the Atlantic led to casualties among warships and merchant ships. US warships began using rubber life rafts. Since the rubber was much higher quality than 35 years before, the inflatable returned, but this time it was boat-shaped.In military use inflatable boats were used to transport torpedoes and other cargo. They also allowed troops to make landings in shallow water, and their compact size and storability made overland transport possible.One of the models, the ZODIAC brand inflatable boat, grew to be popular with the military and contributed significantly to the rise of the civilian inflatable boat industry, both in Europe and in the United States. Zodiac International quickly became and remains the worldwide leading manufacturer of inflatable boats. After World War II, surplus inflatable boats were sold to the public. A version of this boat has been adapted by the Marine Mammal Center for use in rescuing injured marine mammals at sea.[edit] Modern inflatables

An inflatable boat capable of carrying a car. Summer sailing in an inflatable boat.Inflatable liferafts were also used successfully to save crews of aircraft that ditched in the sea; bombing, naval and anti-submarine aircraft flying long distances over water being much more common from the start of WWII. The PBY made by Catalina and Canadair seems to have been the first aeroplane to have had an inflatable life boat aboard, first as optional, later as standard equipment. A later version of that inflatable was pressurized by a gas cylinder rather than by mouth. A wire connected to the plane opened the cylinder valve in the inflatable after the life raft was thrown into the water.Until the middle 1950s inflatables were still rafts in civilian use, hand paddled but the outboard motor came into use in the early 1950s. (The outboard motor was invented in 1909 by Ole Evinrude.)Also in the 1950s, the French Navy officer and biologist Alain Bombard was the first to combine the outboard engine, a rigid floor and a boat shaped inflatable. The former airplane-manufacturer Zodiac built that boat and a friend of Bombard, the diver Jacques-Yves Cousteau began to use it, after Bombard sailed across the Atlantic Ocean with his inflatable in 1952. Cousteau was convinced by the shallow draught and good performance of this type of boat and used it as tenders on his expeditions. Zodiac International quickly became and remains the worldwide leading manufacturer of inflatable boats.The inflatable boat was so successful that Zodiac lacked the manufacturing capacity to satisfy demand. In the early 1960s, Zodiac licenced production to a dozen companies in other countries. In the 1960s, the British company Humber was the first to built ZODIAC brand inflatable boats in the UK.Some inflatables have inflated keels whose V-shape help the hull move through waves reducing the slamming effect caused by the flat hull landing back on the surface the water after passing over the top of a wave at speed.

[edit] Inflatable Boat (small)The inflatable boat (small) is a rubber boat that is in use with several militaries. The inflatable boat (small) can be powered by a small gasoline outboard engine or it can be paddle powered. Paddle powering is utilized when the mission requires a high degree of stealth or when the boat runs out of gas.[edit] Rigid-hulled inflatable boatThe modern rigid-hulled inflatable boat (RIB) is a development of the inflatable boat which has a rigid floor and solid hull. The external shape of the hull lets it cut through waves more easily giving a more comfortable ride when travelling fast in rough conditions. The structure of the hull is capable of supporting a more powerful transom mounted outboard engine or even an inboard engine.Some RIBs may be 14 metres (45 feet) in length and may include inboard steering, luxury features and full cabins.[edit] Inflatable Boat Manufacturers [1]

Rabu, Februari 18, 2009

Amphibious warfare is the utilization of naval firepower, logistics and strategy to project military power ashore. In previous eras it stood as the primary method of delivering troops unto non-contiguous enemy-held terrain. In this modern era amphibious warfare persists in the form of commando insertion by fast patrol boats, zodiacs and mini-submersibles.In the modern era of warfare, an amphibious landing of infantry troops on a beachhead is the most complex of all military maneuvers. The undertaking requires an intricate coordination of numerous military specialties, including air power, naval gunfire, naval transport, logistical planning, specialized equipment, land warfare, tactics, and extensive training in the nuances of this maneuver for all personnel involved.[edit] HistoryRecorded amphibious warfare predates the 18th century by a couple of millennia: the Sea Peoples that menanced the Egyptians from the reign of Akhenaten as captured on the reliefs at Medinet Habu and Karnak, the Helenic city states who routinely resorted to opposed assaults upon each others' shores which they reflected upon in their plays and other expressions of art, the landing at Marathon by the ancient Persians on September 9, 490 BC which history records as the largest amphibious operation for 2,400 years until eclipsed by Gallipoli. More current amphibious landings have been conducted by small commando forces of various states and non-state actors; Israel, Tamil Tigers etc. There exists debate over mainland China (PRC)'s potential to conduct amphibious operations against Taiwan (ROC). With the bulk of the world's population concentrated near the sea, chances are good that future conflict may entail the use of amphibious assets.

The Bayeux Tapestry depicts the 1066 Norman amphibious invasion of England with a force of some 8,000 infantry and heavy cavalry.[edit] 16th centuryIn 1565, the island of Malta was invaded by the Turks. A strategic choke point in the Mediterranean Sea, the loss was so menacing for the Western Europe that forces were urgently raised in order to recover the island. But it took four months to set up, arm, embark and move a 5,500 men amphibious force to the area in battle order.Then, Philip II, King of Spain, decided to permanently assign certain already amphibious skilled Units to the Royal Armada. These units were trained specifically for the fighting on ships and from ships. The Spanish Marines were born. The idea was to set up a permanent assignation of land troops to the Royal Spanish Navy, available for the Crown. Thus, countries adopt the idea and all around the world. Countries raise their Marine Corps too.The first "professional" Marine units were already task-trained amphibious troops, but instead of being disbanded, were kept for the Crown's needs. First actions took place all along the Mediterranean Sea where the Turks and Pirate settlements were a risk for the commerce and navigation: Algiers, Malta, Gelves, La Goleta...Landings as the "Terceras Landing" in Azores Islands 25 May 1583, was a military feat as the planners decided to make a fake landing to distract the defending forces (5,000 Portuguese, British and French soldiers); also special barges were arranged in order to unload horses and 700 artillery pieces on the beach; special row boats were equipped with small cannons to support the landing boats; special supplies were readied to be unloaded and support the 11,000 men landing force strength. The total strength of the amphibious force, was 15,000 men, including an armada of 90 ships.After an initial reconnaissance action where the most suitable beaches for the landing assets were chosen, a 4,000–man first assault wave was unloaded while two "Galeras" made a distractive fake landing away from the main beach. The main defensive body ran to defend against the feinted action, but the first wave had set up a firm defensive perimeter, and the second wave was already landing with the heavy artillery.In this operation we can find documented reports about the detailed planning, the previous reconnaissance of the beaches, the special equipment and training, ship-to-shore movement, naval fire support. Not the first landing, but one of the first amphibious operations.[edit] 17th centuryThis was a century of "expansion". European countries were expanding and creating colonies. Amphibious operations were mostly oriented to settle colonies and strong points along the navigational routes. Fights among countries to keep or destroy opposing power's capabilities were continuous.Amphibious forces were fully organized and devoted to this mission, although the troops not only fought ashore, but on board ships.[edit] 18th centuryAmphibious landings were performed by Spanish Marines allowing them to conquer Sardinia (1717) and Sicily (1732).Not all landings were successful. Mere frontal assaults from the sea against well defended positions could prove a disaster, when they had been planned inadequately.On March 13, 1741, a British fleet, including 2,000 guns in 186 ships commanded by Admiral Sir Edward Vernon, tried to take the Spanish City of Cartagena de Indias with a 23,600–man force, including 4,000 Virginia recruits, commanded by Lawrence Washington (half-brother of George Washington).The defenders lined up 3,000 men, including Marines from the only six ships based in that port.After 15 days of bombing, the British started the landings, delayed by the defenders' actions, and manage to scuttle the six Spanish ships attempting to close the access channel to the city. The defenders were decimated, and only 600 remained inside the last bastion: San Felipe Fortress.

San Felipe de Barajas Fortresses.The Commander of the landing force, General Woork, tried to advance but due to the heavy equipment his forces made only slow progress towards the fortress. The defending artillery focused on the ships supporting troops and the ship-to-shore traffic, while the defenders decimated the advancing troops out in the open. The landing force advance ended abruptly when the attackers found the ladders and engineer equipment was not suitable for the fortress assault.During that very night a carnage took place among the landing force, and with the first light of the morning, a surprising bayonet charge from the defenders finished off the landing force and their supplies.For 30 more days the attackers bombed the fort with no results, and they fell back to Jamaica.In 1759, during the siege of Quebec, the British troops attempted on a number of occasions to cross the Saint Lawrence River in force. An attempt to land some 4,000 troops in the face of resistance failed. Ultimately a landing was managed at a relatively-undefended site, and British troops gained a foothold allowing 5,000 to take part in the Battle of the Plains of Abraham which led to the surrender of the city.In 1776, Samuel Nicholas and the Continental Marines, the "progenitor" of the United States Marine Corps, made a first successful landing in the Battle of Nassau.In 1781, the Spanish field marshall Bernardo de Gálvez, successfully captured British controlled Fort George by ampibious assault in the Battle of Pensacola. In 1782, he captured the British naval base at New Providence in the Bahamas.[edit] 19th centuryDuring the Mexican-American War an amphibious assault was against Vera Cruz in what could be considered the first amphibious assault made by the United States Army. General William J. Worth jumped from the boat and waded to shore in chest deep water and thus could be considered the first U.S. Army soldier to make an amphibious assault.During the American Civil War, the United States made several amphibious assaults all along the Confederate coastline. Hatteras Inlet and Port Royal, South Carolina were the first of many attacks. Along with others on Roanoke Island, NC, Galveston, TX, Morris and James Islands, SC, Fort Sumter, SC and several others. The largest was at Fort Fisher, which was the largest and most powerful fort in the world at the time, protecting the entrance of Wilmington, North Carolina. The assaulting force of over 15,000 men and 70 warships comprising of over 600 guns, was the most powerful amphibious assault in world history and was not surpassed until D-Day 1944.An early form of amphibious warfare was employed during the War of the Pacific in 1879, and saw coordination of army, navy and specialized units.The first amphibious assault of this war took place as 2,100 Chilean troops successfully took Pisagua from 1,200 Peruvian and Bolivian defenders on 2 November 1879. Chilean Navy ships bombarded Allied beach defenses for several hours at dawn, followed by open, oared boats landing Army infantry and sapper units into waist-deep water, under enemy fire. An outnumbered first landing wave fought at the beach; the second and third waves in the following hours were able to overcome resistance and move inland. By the end of the day, an expeditionary army of 10,000 had disembarked at the captured port.Additional amphibious assaults would be carried out thorough the war. By early 1881, Chilean commanders were using purpose-built, flat-bottomed landing craft that would deliver troops in shallow water closer to the beach.Landing tactics and operations were closely observed by neutral parties during the war: two Royal Navy ships monitored the Battle of Pisagua; U.S. Navy observer Lt. Theodorus B.M. Mason included an account on his report The War on the Pacific Coast of South America.[edit] World War I

V Beach, viewed from the SS River Clyde on 25 April 1915.During World War I, amphibious warfare was still in its infancy: tactics and equipment were rudimentary and required much improvisation.During this period, British Royal Marine Light Infantry (merged with the Royal Marine Artillery in the 1920s to form the Royal Marines) were used primarily as naval parties onboard Royal Navy warships to maintain discipline and man ships' guns. The RMLI joined a new Royal Navy division—the Royal Naval Division—formed in 1914 to fight on land; however, throughout the conflict, army units were depended upon to provide the bulk—if not all—of troops used in amphibious landings.The first amphibious assault of the war ended in disaster in 1914. A large British Indian Army force was directed to launch an amphibious assault on Tanga, German East Africa. British actions prior to the assault, however, alerted the Germans to prepare to repel an invasion. The Indian forces suffered heavy casualties when they advanced on the city, forcing them to withdraw back to their boats, leaving much of their equipment behind.The Allied invasion against the Ottoman Empire at the Battle of Gallipoli in 1915 proved even more disastrous than Tanga, in part due to incompetence at the high command.Soldiers were landed via open, oared whaleboats and tugs at Anzac Cove and Helles. At V Beach, Helles, the landing troops—inexperienced at amphibious landings—were effectively slaughtered by the Ottoman defenders, most not even making it out of their landing craft. The Royal Dublin Fusiliers, for example, lost almost all their officers, including their commander, and suffered over 500 casualties.In a second landing at Suvla in August, the forerunner of modern landing craft—the armoured 'Beetle'—was first used by the British.[edit] Interwar periodAlhucemas Landing September 8, 1925, performed by a Spanish-French coalition against rebel Kabilas in the north of Morocco, was a landing where tanks were used for the first time; air naval gunfire support were employed by the landing forces, directed by spotting personnel with communication devices.Floating depots were organized with medical, water, ammunition and food supplies, to be dispatched ashore when needed. The barges used in this landing were the surviving "K" boats from Gallipolli. But in this case, the landings were performed against a prepared, defended in force positions.

[edit] World War II

Troops from the U.S. 1st Division landing on Omaha beach.By the Second World War tactics and equipment had moved on. Purpose built landing craft were used at the evacuation from Dunkirk (Operation Dynamo) and an amphibious operation was tried out at Dieppe in 1942. The operation proved a failure but the lessons hard learned were used later.Arguably the most famous amphibious assault was the Normandy landings on 6 June 1944, in which British, Canadian, and US forces were landed at Utah, Omaha, Gold, Juno and Sword beaches. The organizational planning of the landing itself (Operation Neptune) was in the hands of Admiral Bertram Ramsay. It covered the landing of the troops and their re-supply.Other large amphibious actions in the European Theatre in WWII include:• North Africa • Sicily • Salerno • Anzio • Southern France In the Pacific Theatre, almost every campaign involved "island hopping" assaults from the sea. Some of the famous ones are mentioned:• Battle of Guadalcanal • Battle of Tarawa • Battle of Saipan • Battle of the Philippines • Battle of Iwo Jima • Battle of Okinawa [edit] Post-World War IIDuring the Korean War the U.S. Marine Corps landed at Inchon. Conceived of and commanded by US General Douglas MacArthur, this landing is considered by many military historians to have been a tactical jewel, one of the most brilliant amphibious maneuvers in history[citation needed]. The success of this battle eventually resulted in intervention by Chinese forces on behalf of North Korea. Amphibious landings also took place during the First Indochina War, notably during Operation Camargue, one of the largest of the conflict.[1]The Royal Marines made the first post-WWII amphibious assault during the Suez War of 1956 when they successfully landed at Suez on 6 November. In the Falklands War, the Argentine 1st Marine Brigade,of the Argentine Navy along with Naval Special Forces, landed near Port Stanley on 2 April 1982, while later the Royal Marines' 3 Commando Brigade, (augmented by the British Army's Parachute Regiment) landed at Port San Carlos on 21 May 1982.

Republic of Korea Type 88 K1 MBT comes ashore from a US LCAC.During the Persian Gulf War, a large amphibious assault force, composed of US Marines and naval support, was positioned off the coast of Kuwait and Saudi Arabia. This force was composed of 40 amphibious assault ships, the largest such force to be assembled since the Battle of Inchon.[2] The object was to fix the six Iraqi divisions deployed along the Kuwaiti coast. Due to early misadventure, the mission for this amphibious force turned into a feint. Nevertheless, the operation was extremely successful in keeping more than 41,000 Iraqi forces from repositioning to the main battlefield. As a result, the Marines maneuvered through the Iraq defense of southern Kuwait and outflanked the Iraqi coastal defense forces.The most recent amphibious assault was carried out by the Royal Marines when they landed at the Al-Faw Peninsula on 20 March 2003 during the Iraqi War.

[edit] Comparison to air-mobile operationsSome would contend that Airborne operations have slowly eroded this primacy as larger and more capable air transports have been fielded and that only states with modest airlift potential may view amphibious operations as a viable means of troop deployment. Distinguishing amphibious landing from an airborne landings in the following respects: an airborne landing can take place virtually anywhere, while an amphibious landing must occur on a suitable ocean-facing beach; and an airborne landing in most cases must be supported almost exclusively from the air, while an amphibious landing can be supported by both air and naval shipping.At first sight, in the case of the United States, the first and second Gulf wars, may have given the impression that air transport had supplanted sea transport as a means of moving troops into theatre, this was only possible with the presence of friendly airfields and the absence of an enemy willing and able to contest for air-superiority. In addition, in the aftermath of the First Gulf War, the United States maintained in Saudi Arabia, the heavy weapons and armour (together with a small maintenance cadre) needed to equip its forces for the second Gulf War, being able to fly in troops to join equipment already in theatre. For other, less predictable theatres, the USA maintains a fleet of Forward prepositioning ships in the Sea Basing[3] program. Each group of these ships has the weapons, logistics and equipment needed to support a brigade sized unit for a month, allowing the US to keep its troops in the CONUS and to be flown to which ever theatre they are needed.At present only the United States has the resources and ability of projecting power this way and even this is far from a total supplanting the role of amphibious transports. The one nation in which air-assault was the prime means of long range power projection was the USSR with its VDV, this being primarily a function of it's geography. Even as the largest and best equipped air-mobile force for its day the USSR lacked the airlift capacity to effectively deploy more than a fraction of the VDV in the long range air assault role. The primary limitation of air mobile operations is the vulnerability and availability of suitable airlifters. For strategic missions tankers and long range fighter escorts must be added and most nations do not have these resources making relying entirely on air-mobility for power projection an impossibility.Both air-mobile and amphibious operations have their places, however the truth of the matter is that very few states have the ability to conduct large scale air-mobile operations, and no nation is able of carrying out mass strategic air assault missions into a contested landing zone. Only amphibious forces in conjunction with naval aviation are able to project power into a hostile landing zone at a strength to seize territory and not just raid and harass and to be able to sustain and reinforce such a force until such a time that it can be reinforced by other means.

Selasa, Disember 23, 2008

General uses

Outboard motors for a boat are developed as a self-contained unit with engine, subsidiary systems, and propeller, designed to be mounted at the stern (rear) of the craft. They are the most common motorized method of propelling small watercraft.

As well as providing propulsion, outboards provide steering control, as they are designed to pivot over their mountings and thus control the orientation of the propeller. The transmission leg in the water also acts as a rudder even when the propeller is not providing power.

When boats are out of service or being drawn through shallow waters, outboard motors can also be tipped forward trimmed up over their mounts to elevate the propeller and transmission shaft out of the water to avoid accumulation of seaweed or hitting underwater hazards such as rocks.

Types of motors

The smallest of outboard motors are truly self-contained, with integral fuel tanks and controls mounted on the body of the motor and steered by a "tiller" directly connected to the motor. Such small motors can weigh as little as 12 kilograms (approximately 26 pounds) and provide sufficient power to move a small dinghy at around 8 kts (15 km/h or 9 mph), far faster than possible with oars. They are highly portable, able to be removed by simply loosening their mounting clamps. Small outboards typically use a manual pull start ignition system while larger models often have electric start similar to a car.

Manufacturers have produced large outboard designs, with sufficient power to be used on boats with lengths of 38 feet or longer. The most powerful are Inline-6 and V-8 cylinder blocks rated up to 350 hp.[1]

Manufacturers also produce electric outboards, commonly referred to as "trolling motors", which are used on very small craft or on small lakes where gasoline motors are prohibited, as a secondary means of propulsion on larger craft, and as repositioning thrusters while fishing for bass and other freshwater species in the US, where their quietness and zero emissions outweigh the range deficiencies shared with electric cars. Diesel outboards are also available, but their weight and cost make them impractical for most purposes. An additional issue with diesel outboards is toxic exhaust emissions.

Pump-jet propulsion (replacing the conventional propeller) is available as an option on most outboard motors. Like other types of pump-jet propulsion systems, they offer virtually no cavitation, giving the boat more maneuverability and the ability to operate in very shallow water. However, the low efficiency compared to propellers has seen them restricted to specialized applications.

History and developments

The idea of the outboard was a natural evolution of the canoe. One-off steam designs appeared in the late 19th century in America. While the advent of the two cycle motorbike gas engine created new possibilities. The Waterford outboardengine appears to be the first real, gas outboard that was for sale. Starting with two dozen which were made in 1907, the company went on to make thousands of the units in the next 5 years. The inboard boat motor firm of Caille Motor Company of Detroit were instrumental in making the cylinder and engines. The creation of the first practical and marketable outboardmotor is often credited to Norwegian-American inventor Ole Evinrude in 1909. Between 1909 and 1912 Evinrude made thousands of his outboards and the three horse units were sold around the world. His Evinrude Outboard Co. was spun off to other owners, and he went onto success with ELTO. The 1920s were the first highwater mark for the outboard with Evinrude, Johnson, ELTO, Atwater Lockwood and dozens of other makers in the field.

Historically, a majority of outboards have been two-stroke powerheads fitted with a carburetor due to the design's inherent simplicity, reliability, low cost and light weight. On the negative side of the balance sheet, conventional two-stroke outboards are notorious polluters due to the high volume of unburned hydrocarbons (unburned gasoline/petrol) in their exhaust. They are also loud as anyone near a leafblower knows.

In the 1990s US and European exhaust emissions regulations led to the proliferation of four-stroke outboards. Though fewer in number, four-stroke outboards have always been available. For example Honda Marine has been marketing small four-stroke outboards since the early 70s. Other brands have been produced for over a 100 years, but again in fewer numbers.

Mercury Marine, Mercury Racing, Honda Marine, Suzuki Marine, and Yamaha Marine,China Oshen-Hyfong marine have all developed new four-stroke engines. Some are carbureted, usually the smaller engines. The balance are electronically fuel-injected. Some models benefit from variable camshaft timing, and multiple valves per cylinder. Mercury Verado four-strokes are unique in that they are supercharged.

Mercury Marine, Mercury Racing, Tohatsu, Yamaha Marine, Nissan and Evinrude each developed computer-controlled Direct-Injected two-stroke engines. Each brand boasts a different method of DI. Fuel economy on both direct injected and four-stroke outboards measures from a 10 percent to 80 percent improvement, compared with conventional two-strokes. Depending on rpm and load at cruising speeds figure on about a 30 percent mileage improvement.[2]

Outboard motors benefit from the ability to draw coolant from the water, obliviating the need for radiators and cooling fans, thereby simplifying the design and lowering component weight.